HD3SS6126: Can the chip return be -DIFFERENT- than the diff pair return

this device is designed for  USB application, one pair is for USB2 (DP/DM), one pair for USB3 TX+/-, one pair for USB3 RX+/-. Can you explain more about what you want to do?

my pcb has impedance control as a microstrip with a plane for return.

does the chip expect the same return on its ground pins as the pcb?

thanks!

your PCB return path should be good enough, nothing special for 6126.

The chip does not implement a microstrip impedance matching?

I guess they could be just coupled to each other only.

Kindly confirm!

no, switch device is a path with low impedance.

how much isolation does it offer between ground and diff pairs?

please see the attached drawing showing different grounds!

best.

based on S parameter model, crosstalk is -35db and isolation is -23db, is this good enough?

Kindly confirm my understanding!

-23dB is power (0.5%) transfer between return and diff pair

how do i get to impedance, power is inversely proportional?

(ignoring the above problem) impedance to the return must be ~18k ohms because 18k || 90 ohm = 90 ohm + 0.005%

what is the single ended characteristic impedance inside the chip?